Electric resistance unit.



H. W. DENHARD.

ELECTRIC RESISTANCE UNIT.

APPLICATION FILED OCT. 3l. 1911.

1,143,577. Patented June 15, 1915.

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UNITED sTATEs PATENT oEEIoE.

HARRY w. DENHABD, or SAN FRANCISCO, CALIFORNIA.. SIGNOR TC THE CUTLER- HAMMER um. Co., or MILWAUKEE. WISCONSIN, a CCRPCBATIQN or WISCONSIN.

Application led October 81,1811.

To all whom it may concern Be it known that I, HARRY W. DENIIARD, a citizen of the United States, residing at San Francisco, in the county of San Francisco and State of California, have invented new and useful Improvements in Electric Resistance Units, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

My invention relates to electric resistance units.

It has among its objects to provide an improved electric resistance unit.

A further object of my invention is to provide an improved resistance unit espe.- cially adapted to use in connection with electric heating devices, which may be made up in a very compact and rugged form and may be readily inserted in the object to be heated as a complete device adapted to give a uniform heat to all of the parts of the object to be heated.

Other objects and advantages of my improved construction Will hereinafter appear.

In the accompanying drawings I have, for purposes of illustration, shown one form which my invention may assume in practice. My invention is not, however, limited to this form but may assume various other forms.

In the view of these drawings: Figure l shows a top plan view of a heating unit. Fig. Q shows a side elevation of the unit shown in Fig. 1. Fig. 3 shows a sectional view of line 3 3 to Fig. l. Fig. 4 shows a sectional View of line 4 4 to Fig. l.

In these drawings I have, for purposes of illustration, shown my improved electric resistance unit adapted for use as a heating element for electric laundry irons. As illustrated in these drawings, a resistance material 1 is preferably wound upon an insulating base 2 and inclosed between sheets 3 and 4 of a suitable insulating material which may be slightly larger than the base 2, and which like the latter are formed of such a shape ythat they may be readily inserted within the body of an iron. The sheets 3 and 4 are preferably ,held snugly against the resistance wire l and the base 2 by means of suitable attachment devices, such as rivets 5, and at .the back of the unit suitable terminal plugs 6 are preferably provided.

AS illustrated in Fig. 1, the insulating Specification of Letters Patent.

Patented June 15, 1915.

Serial No. 857,805.

base 2 is preferably provided with a plurality of ears 7 on its curved sides, which are separated by notches 8 preferably having rounded portions 9 on the opposite sides of the-1r inner ends. The center of the base 2 is preferably provided with a cutaway portion 10 of any suitable width preferably provided with similar ears .and similar notches. This cutaway portion preferably extends from a point near the tip of the unit to a point adjacent to the back of the same and near the terminal plugs 6. If desired the ears near the middle and back of the unit may be slightly more peaked than those near vthe tip. In a preferred form a portion of the base 2 around the terminal pugs .6 is left unslotted, as shown in Fig. 1.

-owever, at the opposite sides of this uni`slotted portion suitable ears similar to the ears 9 are provided. As illustrated in Fig. l, suitable notches 11 are preferably provided on the opposite sides of the base 2 and at the back of the same.

The resistance material l, which may assume the form of a refleXed resistance wire, is wound or looped upon the base 2 in such a manner as to form a continuous circuit from .one of the terminal plugs 6, back and forth across one side of the unit, passing first through one of the notches 11, then through one of the notches adjacent to the terminal plugs A6, back to one of the outer notches 8, and from this notch successively back and forth to the tip of the iron, Where it is brought across to the other half of the base and passes downward back and forth across that half in the same manner until it reaches the other terminal plug 6. It is to be noted that with the resistance material distributed as it is shown in Fig. 1, the heating capacity of the unit is greatest at its tip, since there is at the tip a greater amount of resistance material in proportion to the amount of surface to be heated. Further,

it is to be noted that at the sides of the unit the resistance wire is so arranged as to give the .desired increased heating effect to the sides of an iron, while at the back where there is no great necessity for heat there is a smaller amount of resistance material. As

in the usual construction, the unit may be arranged to be held in position within an iron by means of suitable bolts which clamp the same between the bed portion of the iron and the heat retaining plate. These bolts may pass down through suitable registering perforations 12 in the several sheets of 1nsulation on opposite sides of the unit and 1n a preferred form are insulated fr om the resistance material by slightly spacing the reflex portions of the Wire around the same, as shown in Fig. 1. In order that the Wire may be brought back around these bolts, it 1s preferablyrelexed somewhat diagonally as shown in that figure, so that the uniform heating effect of the same is not disturbed.

At the back of the iron the ends of the resista-nce material are preferably brought through the notches 11 over to a point behind the terminal plugs 6 Where they are passed through suita le perforations or slots 13 in the base 1 and are preferably reliexed through one or more turns before. being brought to the underside of the terminal plugs 6. These terminals are shown 1n Flg. i in enlarged section;4 and in a preferred form consist of substantially cylindrical members having central plug receptacles 15 arranged to receive any sultable termmal plug, suitable flanges 16 being provided on their lower ends. As illustrated in this ligure, the cylindrical member 6 preferably passes through a perforation 17 in the upper insulating sheet 3 Which is of a smaller diameter than the flange 16, so that the terminal plug is securely held in position. The end ofthe resistance Wire 1 is attached to the terminal plug 6. In a preferred form this Wire is attached to the plug by means of a smaller removable plug 18, which may be inserted in the lower end of the cylindrical member 15, a suitable clearance being provided so that when the plug member 18 is forced in, it may wedge the end of the wire 1 between itself andthe inner wall of a suitable opening in the member 6. If desired the plug member 18 may be integral with the flange 16 or may be separate from the same, or this iiange member may be a distinct element which is held in place by the plug 18.

By my improved construction I have provided an electrical resistance unit which may be made up`into its iinished form With the terminal connections thereon and when so assembled constitutes a complete unit of an exceedingly rugged construction which will withstand rough handling. The two inclosing sheets of insulation are snugly fitted down over the insulating base carrying the resistance material and serve to adequately protect and insulate the resistance material and to prevent the displacement of the same in such a manner as to cause short circuits. Further, the ears formed on the insulating base are fully protected so that they may not readily be broken. Further, by compressing these insulating sheets snugly upon the resistance material the heating efficiency of the unit is materially increased. By the provision of my improved manner of distributing the resistance material a uniform heat is provided and loss of heat at the sides and tips of the devices to be heated is compensated for in a satisfactory manner. Further, by the provision of my improved construction and arrangement of terminal plugs, these plugs are securely held in position in the unit and in connection with the resistance material so that they may not be readily separated. Further, by my improved construction I have been able to provide an exceedingly rugged and unitary heating element which may be manufactured at small expense.

lVhile I have in this application, for purposes of illustration, shown and described my invention as applied to an electric laundry iron, my invention is not limited to this use but may be adapted to various other uses wherein the heating element assumes various forms. Consequently, I do not Wish my invention to be limited to the specific construction herein described for purposes of illustration, but Wish rather to include within its scope all of those forms and adaptations of the same falling Within its spirit.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric resistance unit, a plurality of sheets of insulation, an insulating base, a re'lexed resistance material Wound upon said base and engaging portions thereof, means for connecting said sheets of insulation and compressing the same upon said base to form a unitary structure, and terminal receptacles carried by said unit.

2. In an electric resistance unit, a plurality of sheets of insulation, an insulating base, a refiexed resistance material Wound convolutions on said base and engaging portions thereof, rivets connecting said sheets of insulation and compressing the same upon said base and resistance wire, and flanged terminal plugs having their fianged ends resting upon said base and their plug ends extending through perforations in one of said sheets of insulating material.

3. A complete electric resistance unit comprising an insulating base having a resistance material carried thereby and terminal plugs mounted thereon, said base having a central longitudinal opening whereby it is divided substantially into two equal parts, said resistance material being Wound back and forth on each of said parts and being connected to said terminal plugs, and sheets of insulating material secured to each other through said central opening.

4. A resistance unit having an insulating base provided with notches on its outer edges, av central longitudinal opening in said base having notches'in its edges, and a resistance material Wound back and forth on one side of'said base from the notches in the edges of the base to the notches in the edges of the opening.

5. In an electric resistance unit, a plurality of sheets of insulating material, an insulating base having ears formed thereon, a reiexed resistance material wound in convolutions upon said base and engaging said ears, and means extending through said sheets of insulation for compressing the same upon the opposite sides of said base to form a unitary structure.

(i. In an electric resistance unit, a plurality of sheets of insulating material, an insulating base having ears formed thereon, a

[SEAL] Corrections in Letters Patent No. 1,143,577.

relexed resistance material wound in convolutions upon one surface of said base and engaging said ears, and rivets extending through said sheets of insulation and compressing the same snugly upon said base and resistance material to form a unitary structure.

In Witness whereof, I have hereunto subscribed my name in the presence of two witnesses.

HARRY W. DENHARD.

Vitnesses:

WV. L. ROCKWELL, GEO. B. JONES.

It is hereby certified that in Letters Patent No. 1,143,577, granted June 15, 1915,

upon the application of Harry W. Denhard, of San Francisco, California, for an improvement in Electric Resistance Units, errors appear in the printed. specification requiring correction as follows: Page A2, line 106, for the Word material read wire; and same page and line, -after the lWord Wound insert the word in; and that the said Letters Patent should be read with these corrections thereinithat the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of July, A. D., 1915.

R. F. WH'ITEHEAD,

Acting Uommiss'ioucr of Patents. 

